At each given moment in time, the Moon is no closer than 361,000 and no further than 403,000 kilometers from the Earth. In addition, the Moon is small - gradually moving away from the Earth by an average of 5 centimeters per year. For many centuries, people have been observing the gradually waning moon. A day may come when the Moon breaks off from the Earth and flies into space, becoming an independent celestial body. But this may not happen. The balance of gravitational forces holds the moon tightly in Earth orbit.

Interesting fact: The moon annually moves away from the Earth by about 5 centimeters.

Why is the moon moving away from the earth?

Any moving body wants by inertia to continue its path in a straight line. A body moving in a circle tends to break from the circle and fly tangentially to it. This tendency to break away from the axis of rotation is called centrifugal force. You feel centrifugal force in a children's park, riding a high-speed swing, or when driving a car, when it turns abruptly and presses you to the door.

The word "centrifugal" means "running from the center." The moon also seeks to follow this force, but it is held in orbit by the force of Earth's gravity. The moon remains in orbit because the centrifugal force is balanced by the force of Earth's gravity. The closer its satellite is to the planet, the faster it rotates around it.

What is the reason? Any moving object has a moment of momentum.The moment of a rotating body depends on the mass, speed and distance from the axis of rotation. The moment can be calculated by multiplying these three values ​​among themselves. Scientists have found that the moment of rotation of this body does not change. Therefore, when an object approaches the axis of rotation, it, by virtue of the law of conservation of momentum, will rotate faster, since the mass in this equation cannot be changed arbitrarily.

Reasons for the Moon

This law, called the law of conservation of torque. The moon makes one revolution around the earth in about 27 days. But 2.8 billion years ago, the Moon closer to us circled the Earth in 17 days. According to Clark Chapman, an astronomer at the Planetary Science Institute in Tucson, Arizona, the Moon was once even closer. At the time of the formation of the Lunar Earth 4.6 billion years ago, the lunar orbital period was only 7 days. If then anyone could see the moon, he would be struck by the enormous size of the rising blood red moon.

Tide of oceans

Surprisingly, the tides of the oceans - this is the same force that pushes the moon from the earth. It happens like this. The gravitational force of the moon acts on the waters of the earth's oceans, attracting them. But the Earth does not stand still - it rotates around its axis. When the waters of the ocean swell, rushing toward the Moon, the Earth, as it were, rotates, as it were, tears this mass of water from it.

In this case, the gravitational force of ocean water attracts the Moon, but not directly to itself, but slightly forward, along the rotation of the globe. Therefore, the moon receives an impulse directed not strictly along the radius of its orbit, but along the tangent to it. This phenomenon lengthens the orbit of the moon. With the imperceptible (month after month) lengthening of the lunar orbit, the Moon is small - gradually moving away from the Earth.The process is very slow and invisible to the eye, but it lasts millions of years and the total result is very noticeable.

Probably someday the Moon will be so far from the Earth that the force of Earth's gravity will weaken, and the Moon will be able to go on an independent flight around the Sun. However, scientists believe that such loneliness of the moon is unlikely to threaten. After all, the tides act on the Earth too. The movement of the masses of ocean water slows the rotation of the Earth, so for 100 years the day increases by about half a minute. (Billions years ago, the day lasted no more than six hours.)

Perhaps billions of years ago, the moon revolved around the earth in just 7 days.

In the future, after millions of years, the duration of the day and the time of one revolution of the Moon around the Earth will still be equal, but already far exceed twenty-four hours. When the Moon moves far enough away from the Earth, their rotations will be more synchronized and the tides of the oceans will be exactly under the Moon. Then the gravity of the water will have an attractive effect on the moon, and it will cease to move away from the earth. The process will go in the opposite direction, when the tidal regions are behind the moon. The orbit of the moon will begin to shorten, and it will gradually approach the Earth. Maybe there will come a time when the huge moon will appear again in the sky.